As integrated circuit geometries shrink, the resolution must be improved for optical systems which may be used in such applications as inspection systems and circuit probe and/or repair systems. Many probe systems used for complex circuitry having multiple metallization layers utilize backside probing and imaging. A description of a backside probing system including backside imaging is found in U.S. Pat. No. 6,518,571, issued Feb. 11, 2003. For backside imaging and probing through silicon, the transmission window of silicon combined with electro-optical effects in silicon restrict the useable optical wavelengths to the near infrared (NIR) region (900 nm to beyond 2000 nm). Thus, whereas for lithography applications optical resolution can be improved by moving to shorter wavelengths, for many probing applications the wavelengths are restricted and the optical resolution improvement cannot be achieved by this method. The most practical alternative for improving optical resolution for probing applications is to increase the numerical aperture (NA) of the objective lens used for focusing light onto the Device Under Test (DUT) and for collecting light from the DUT.
Prior methods for achieving high NA for imaging/probing systems have inherent drawbacks. One serious drawback is the high cost of high NA lenses (NA>1). A well-known type of high NA lens, the Solid Immersion Lens (SIL), tends to have a small field of view and is very difficult and costly to design with a reasonable field of view. It is also difficult to design a SIL that is apochromatic (color corrected over a range of wavelengths).
It would be a significant advance in optical systems for probe applications to provide a high NA, large field of view optical system which could be utilized for a wide range of applications such as: 1) optical probing applications, one example being laser probing applications, 2) photon emission timing analysis applications, and/or 3) applications such as TIVA/LIVA, (Thermally Induced Voltage Alteration/Light Induced Voltage Alteration), OBIRCH/OBIC (Optical Beam Induced Resistance Change/Optical Beam Induced Current), and RIL (Resistive Interconnection Localization) wherein the “image” is formed by monitoring either the DUT or a tester connected to the DUT, rather than being formed from the reflected laser light. It would be of further benefit to provide a hybridized method of combining traditional imaging with a low field of view lens, combined with imaging with a high NA, large field of view optical system in order to provide increased speed for the imaging operation.